Hybrid couplers are used in many types of radio frequency (RF) circuits, such as duplexers, multiplexers, balanced amplifiers, transmit/receive switches, and/or the like. A hybrid coupler is a device that splits an RF signal into quadrature hybrid signals (QHSs). Unfortunately, hybrid couplers may have limited quality (Q) factors, thus passing undesired harmonics into the QHSs. As such, additional RF filters are often used to filter the undesired harmonics out of the QHSs. However, these additional RF filters introduce additional insertion losses.
Thus, designs for hybrid couplers that are capable of filtering out undesired harmonics from the QHSs are needed.